The T/t-complex is a region of mouse chromosome 17 defined by aberrant t haplotypes which occur naturally in wild populations. These t haplotypes exhibit a series of effects on development, spermatogenesis, and meiotic recombination. The genetic basis for these effects is complex, and with one exception (p62/6.9-like genes, and to approach the molecular basis for the functional non-homology which exists between wild-type and t-haplotype DNA/chromatin. Second, we will construct mouse strains which are congenic for a series of t haplotype fragments and T/t-region deletions on a single inbred background. These strains will be used to correlate specific molecular differences with specific t haplotype factors that affect embryogenesis and spermatogenesis. Third, we will use a computer-analyzed two-dimensional system of gel electrophoresis to identify, map, and characterize the expression of proteins coded for or affected by the T/t-complex. As a long range goal, we hope that these investigations might provide some insight in to particular mechanisms of differentiation in mammals.